Wednesday, 27 July 2016

Globe cooled when CO2 was Eight Times current concentration.

If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2will need to be reduced from its current 385 ppm to at most 350 ppm.

Right now we're at 400 ppm, and we're adding 2 ppm of carbon dioxide to the atmosphere every year.Unless we are able to rapidly turn that around and return to below 350 ppm this century, we risk triggering tipping points and irreversible impacts that could send climate change spinning truly beyond our control.

Source : Nature CommunicationsTo find appropriate species, we choose two regions with similar climate, one from a simulation with today’s climatic and CO2forcing and another from an Ordovician simulation with a high atmospheric CO2 value of 24 PAL.

AND YET, in a paper published this month, we learn that in the Late Ordovician (450Ma) CO2 concentration was 2240ppm and perhaps 6720ppm (24 PAL) as in above diagram.

Globe cooled when CO2 was Eight Times current concentration.

During the Ordovician period, the concentration of CO2 in Earth's atmosphere was about eight times higher than today. It has been hard to explain why the climate cooled and why the Ordovician glaciations took place.

So, if Hansen and McKibben are wrong about the tipping point, what is the ideal concentration of CO2 in the atmosphere? As reported by Joanne Nova, 60 years ago a paper was published that showed that the then concentration of CO2 was almost at starvation level for a corn field in the morning sun.

An acre of corn is a living machine drawing CO2 from the air around it. In windless conditions, CO2 concentrations over a cornfield build up each night as CO2 diffuses from higher air and the organic matter and bacteria create CO2 from the soil. A paper by Chapman et al from 1954[1], shows that as soon as the sun comes up, to power-up those dormant photosynthetic cells, the plants rapidly draw down as much CO2 as possible, and when the CO2 levels fall too low, plant growth surely slows.

On a windless day CO2 values rose to 410ppm overnight and fell to 210ppm during the morning.

This graph shows CO2 content of the air over a cornfield on a still day (no wind). Sunrise occurs at 5am and CO2 levels plummet til 8am, reaching their lowest by 1pm, which is nearly half the CO2 concentration of the peak reached overnight. The corn is affecting CO2 levels in air even as high as 150m or 500ft above. These level out by around 8am and only start to increase again, a couple of hours after sunset.